Materials Characterization Paper 

In Support of the 

Final Rulemaking: 

Identification of Nonhazardous Secondary Materials That Are Solid Waste 

Spent Solvents and Related Materials 

February 3, 2011 

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1. Definition of Spent Solvents 

A solvent is a material used to dissolve or dilute another substance. Examples of solvent use 

include degreasing, cleaning, and fabric scouring, use as diluents, extractants, and reaction and 

synthesis media. A spent solvent is a solvent that has been used at least once and cannot be used 

again for its original purpose without being processed, due to contamination during its use. This 

analysis addresses only solvents that: 1) have potential fuel value (i.e., organic solvents), and 2) 

are not considered hazardous under RCRA. Specifically, this paper targets non-hazardous, nonhalogenated, solvents. Non-halogenated solvents include a variety of organic chemicals 

(hydrocarbons, alcohols, ketones, esters, etc). 

2. Annual Quantities of Spent Solvents Generated and Used 

(1) Sectors that generate spent solvents: 

• A wide range of non-hazardous spent solvents are generated by a large number of 

industries. Generators of spent solvents can include industries that use solvents, 

industries that recycle or process spent solvents from other sources, and, in some 

cases, industries that manufacture solvents. Facilities in the following NAICS 

industry sectors focus specifically on the manufacture or management of solvents: 

325998 – Recycling services for degreasing solvents (e.g., engine, machinery) 

manufacturing; 325132 – Solvent dyes manufacturing; 324110 – Solvents made in 

petroleum refineries; and 811111 – Automotive repair and replacement shops. 

• Solvents are typically used in the following industries and applications: coatings, 

cleaners, inks, adhesives, pharmaceuticals, agricultural and food uses, personal 

care, automotive, microelectronics, and aerosol products (American Chemistry 

Council 2008). 

(2) Quantities and prices of spent solvents generated: 

• Due to the wide variety of solvents produced and used, it is difficult to 

characterize the quantity or prices of spent organic non-hazardous solvents 

generated in the U.S. Only a fraction of all solvents produced return to the market 

as spent solvents; many are recycled and reused on site by generators. Total 

annual production of solvents exceeds 10 billion pounds (5 million tons) per year 

(Paint and Coatings Industry 2006). This suggests that the total quantity of 

solvents that require replacement could also be roughly five million tons per year. 
Spent Solvents and Related Materials 

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• The limited information available on markets for spent solvents focuses on 

hazardous solvents; these are commonly used as fuel, and they are “priced” to be 

less expensive to the generator than the avoided cost of hazardous waste disposal, 

which can range from $0.41 to $2.13 per gallon (Environmental Technology 

Council 2004). 

(3) Trends in generation of spent solvents: 

• Information on trends in generation of spent solvents is difficult to assemble given 

the range of products and management options. National demand for solvents is 

expected to rise by one percent a year to 12.5 billion pounds in 2010 (Paint and 

Coatings Industry 2006). However, as interest in recycling, reuse, and waste 

minimization increases, and the costs of reuse decrease, this projection may not 

hold. 

3. Uses of Spent Solvents 

(1) Combustion uses of spent solvents: 

• Solvents with sufficient calorific value and minimal contamination can be readily 

used as fuel in a range of boilers, furnaces, and kilns. However, readily available 

information suggests that non-hazardous solvents do not represent a significant 

alternative fuel source. 

• Portland Cement Association data indicated that the BTU value per pound of 

spent solvent varies due to the wide variety of solvent types (Portland Cement 

Association 2007). 

• Solvents that are considered hazardous under RCRA frequently have fuel values 

that are similar to coal. Hazardous waste, as estimated by the Assessment of the 

Potential Costs, Benefits, & Other Impacts of the Hazardous Waste Combustion 

MACT Final Rule Standards, and the Economic Analysis for the Proposed 

Emission Comparable Fuel rule (based on the information contained in the 

hazardous waste constituent survey), has a heating value between 12,200 and 

13,500 Btu per pound. In fact, a number of these solvents appear to meet the 

definition of hazardous waste because they are characteristic for ignitability, 

suggesting that there is a strong correlation between hazardous solvents and high 

fuel-value solvents. This may suggest that non-hazardous solvents are typically 

less valuable as a fuel source, but the variation among solvents makes it difficult 

to draw any specific conclusion. 

(2) Non-combustion uses of spent solvents:

• Most spent solvents can be reprocessed and recycled for use again in their original 

form. Facilities that produce spent solvents may choose to install recycling 

equipment in an effort to cut costs on virgin solvent purchases (see, for example, 

Ohio EPA 2004; and NSBDCBEP). It is difficult to estimate the quantities of nonhazardous spent solvents disposed or kept in storage because they originate in 

many locations, and are likely managed in a number of different ways. It appears, 

however, that recycling is a viable option for a significant percentage of nonhazardous solvents.
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4. Management and Combustion Processes 

(1) Types of units using spent solvents

• It is possible that some non-hazardous, organic, solvents may have Btu values that 

would give them value as a fuel source. Hazardous solvents, whose generation 

and management is tracked in the Biennial report, are burned as fuel in a variety 

of liquid-fuel industrial boilers and cement kilns. 

• One limitation concerning burning solvents may be the design of combustion 

equipment. Bullard (2007) notes that boiler and burner manufacturers and other 

companies that support commercial and industrial boilers have only limited 

experience with burning hazardous or non-hazardous waste solvents. These 

boiler/burner supportive industries are more familiar and more interested in 

working on projects involving traditional fuels like natural gas and distillate, since 

this is the fuel overwhelmingly in use in industry (Bullard 2007). 

• Cement kilns are experienced at burning hazardous waste solvents, along with a 

range of other liquid wastes. However, an industry contact noted that EPA’s 

introduction of the exclusion rules in the 1990s that removed materials with high 

Btu values, when used as fuels, from the definition of solid waste, have resulted in 

more energy recovery from solvents on-site at manufacturers; as a result, solvents 

have diminished as a fuel source in the cement industry (Guerra 2008). 

• An EPA document source concerning industry impact information of boilers 

suggests that some nonhazardous waste burning cement kilns use, among various 

other secondary fuels, spent lubricants and solvents (EPA 2008b). These data are 

not sufficiently broken down to attribute any energy savings information to spent 

solvents specifically. 

(2) Sourcing of spent solvents:

Spent solvents originate in many locations, and a national-level collection and 

distribution system does not exist for all types of solvents. However, census data 

indicates that recycling of solvents is widespread. Recycling services for degreasing 

solvents (e.g., engine, machinery) manufacturing includes 1,188 facilities that are 

involved in the management of secondary solvents. This does not address the on-site 

recycling and fuel recovery activities that take place at generators. 

(3) Processing of spent solvents: 

In some cases, only minimal processing is required to reuse spent solvent on site, 

since it is not always necessary to have 100 percent purity (Ohio EPA 2004). 

Alternatively, some types of solvents may not be suitable for reuse even after 

significant processing (including physical and chemical processes to remove 

impurities) and therefore must be managed through an alternate method, including 

being used in a different process or sold to another company for use. 
Spent Solvents and Related Materials 

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(4) State regulatory status of spent solvents use as ingredient: 

At this stage, we have not identified any states that have specifically granted a 

beneficial use designation for the use of spent solvents as fuel, but we have not 

performed an exhaustive investigation of state activities and regulations. 

5. Commodity Composition and Impacts 

(1) Composition of spent solvents: 

The composition of spent solvents can vary widely depending on the original 

chemical structure and the solvent, and the substance with which it was first used. To 

be useful as a non-hazardous fuel source, solvents must have carbon (i.e., be organic). 

However, other constituents are difficult to characterize because they are based 

largely on the specific process (e.g., cleaning production equipment) in which the 

solvent was originally used. 

(2) Impacts of spent solvents use:

• Data from the Portland Cement Association notes that the Btu value per pound of 

spent solvent varies (Portland Cement Association 2007), but when it can be used 

as an alternative fuel, it offsets use of primary fuels. 

• Benefits associated with use of spent solvents as fuel include avoided risks 

associated with disposal, cost savings associated with avoided disposal and 

recovery of energy, and the avoided environmental impacts associated with 

production of energy from “virgin” non-renewable sources when solvents are 

used instead.1

• The specific lifecycle impacts of spent solvents used as a fuel are not evaluated 

here because of uncertainties in lifecycle scenario development. For example, it 

is difficult to identify the fuel (Btu) value and emissions factors associated with a 

“typical” non-hazardous organic solvent that is suitable for fuel. In addition, spent 

solvents may substitute for a variety of fuels; the choice of fuel often depends on 

location specific-factors such as the location of the combustor in relation to fuel 

supplies, and on the design of the specific combustion unit. Avoided upstream 

impacts depend heavily on the specific fuel being displaced in the lifecycle 

scenario. 

 1 With respect to the costs associated with beneficial use, cement kiln operators are generally required to 

enact performance testing and air permit modifications prior to using scrap tires and other alternative fuels. In 

addition, kilns may be required to install continuous emissions monitoring systems if they chose to burn scrap tires 

(EPA 2008a)
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References 

Personal Communication with Erika Guerra, Holcim Ltd., August 26, 2008. 

American Chemistry Council, “Solvents Industry Group: Solvents Explained.” 2008. Available at 

http://www.americanchemistry.com/s_acc/sec_solvents.asp?CID=1483&DID=5586 

Bullard, Jack L., P.E. “Determining the Technical Feasibility of Firing Waste Solvent in an Existing Industrial or 

Commercial Boiler.” Continuing Engineering Education Journal. Article #0015. 2007. Available at: 

http://www.ceejpublishing.com/Articles/0015.htm 

Environmental Technology Council, “May 2004 Incinerator and Landfill Cost Data,” 2004. Available at: 

http://www.etc.org/costcurvey8.cfm 

Nevada Small Business Development Center Business Environmental Program (NSBDCBEP), “Solvent Recycling 

at Crumrine,” CS- FY9501018. Available at: www.nsbdcbep.org/pdf/case/Crumrine.pdf 

Ohio EPA, “Onsite solvent recycling equipment,” Office of Pollution Prevention. September 2004, Number 9. 

Available at: www.epa.state.oh.us/opp/solvents/fact9.pdf 

Paint and Coatings Industry, “U.S. Solvents Demand to Exceed 12 Billion Pounds in 2010,” July 1, 2006. Available 

at: http://www.pcimag.com/Articles/Industry_News/515aaeb98e85c010VgnVCM100000f932a8c0____ 

Portland Cement Association, “Beneficial Reuse of Materials in the Cement Manufacturing Process.” PCA R&D 

Serial No. 2868. p. 8. 2007. 

United States Environmental Protection Agency, (EPA). 2008a, Cement Sector Trends in Beneficial Use of 

Alternative Fuels and Raw Materials, October 2008. 

United States Environmental Protection Agency (EPA). 2008b, “Identification of Nonhazardous Materials That are 

Solid Waste. EPA Exhibit 1: Preliminary Estimate of Total Non Hazardous Secondary Materials Used 

Annually in Boilers and Kilns. Sept. 24, 2008